I think the whole day in Disney is enough. So, your kids will enjoy themselves. Ramada Kowllon Hotel is about 10-15 minutes walking from the nearest MTR station, Tsim SHa Tsui (Exit B1). Take mtr and get off at the next stop, Admiralty. Get out from Exit B and there is bus 629 to Ocean Park directly. There is also a ticket office of Ocean Park here. You can buy ticket here to avoid making lines at the entrance of Ocean Park.
It costs 4RMB per person for the MTR and 10.6HKD for Bus 629. Kids 3-11 years old pay half of the price.